Implement deref coercions. #21351
Implement deref coercions. #21351
Conversation
|
r? @pnkfelix (rust_highfive has picked a reviewer for you, use r? to override) |
c518f9e
to
b4febf8
Compare
|
💃 |
|
@nikomatsakis I'm not sure I'm the best person to review this. Maybe @nick29581 ? |
|
Do you know what change made all the coercion cruft in commit three obsolete? Do we have tests to ensure nothing has regressed here? |
|
LGTM. I'd like to see a few more tests - in particular some more compile fail tests to check we don't allow anything we shouldn't. The rpass tests look OK, I think we should probably have some more to check more extreme edge cases - coercions equivalent to And of course we need to wait for the RFC to land |
|
The removed trait object coercions were dead code, the cases are handled by |
|
FYI: The RFC has been merged. |
|
|
||
| use std::rc::Rc; | ||
|
|
||
| // Examples from the "deref coercions" RFC, at rust-lang/rfcs#241. |
There was a problem hiding this comment.
I'd like to see some negative tests for borrow checker failures.
For example, passing the same &mut Box<T> value for two distinct &mut T arguments.
There was a problem hiding this comment.
Also, passing to one &T and one &mut T argument.
There was a problem hiding this comment.
And one like this:
fn copy<T>(x: &mut T) -> &mut T { x }
fn foo<T>(x: &mut Box<T>) {
let y = copy(x);
let z = copy(x); // ERROR (I hope)
}There was a problem hiding this comment.
And one like this:
fn copy<T>(x: &T) -> &T { x }
fn foo(x: &mut Box<int>) {
let y = copy(x); // OK
let z = copy(x); // OK
**x += 1; // ERROR, borrowed
}b4febf8
to
e6064dd
Compare
e6064dd
to
46696c8
Compare
|
@bors r+ 46696c84fd2d2459186252657bcf1e76428c5043 |
|
The coercion logic around unsafe pointers in particular looks strange to me, but that seems to be a pre-existing problem. e.g. this line here https://github.com/eddyb/rust/blob/67718004499d1e446eef4def35aeafc8bf4c0858/src/librustc_typeck/check/coercion.rs#L235 is strange, since it seems to only permit coercions from |
|
⌛ Testing commit 46696c8 with merge 40c00b4... |
|
💔 Test failed - auto-mac-32-opt |
|
@bors retry q_q |
|
☔ Merge conflict |
46696c8
to
ae076e1
Compare
|
⌛ Testing commit ae076e1 with merge 398ac8f... |
|
💔 Test failed - auto-win-32-nopt-t |
|
@bors retry |
Coercions will now attempt to autoderef as needed before reborrowing. This includes overloaded `Deref`, e.g. `&Rc<T>` coerces to `&T`, and `DerefMut`, e.g. `&mut Vec<T>` coerces to `&mut [T]` (in addition to `&[T]`). Closes #21432.
Coercions will now attempt to autoderef as needed before reborrowing.
This includes overloaded
Deref, e.g.&Rc<T>coerces to&T, andDerefMut, e.g.&mut Vec<T>coerces to&mut [T](in addition to&[T]).Closes #21432.